Police that year said 55 people lost $1.7 million to scammers in Malaysia, but the Postal Workers Union says that's just the tip of the iceberg.

"How many people were scammed and never came forward, we don't know," says president John Maynard.

Scratchies parcelled with glossy travel brochures are being posted mostly to the elderly, promising thousands in winnings.

"They're told they need to pay an amount of money to Malaysia in local tax and legal costs to have their prise released," says Maynard. "We're aware of one person that was scammed of $64,000."

Other victims include a retired police officer and a woman "with multiple university degrees" who lost $18,000.

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Maynard says old age homes are being targeted as the elderly are more trusting, and embarrassed victims are not coming forward.

"We want people to have some way of being aware that what's coming through their boxes is an attempt to defraud them. We've had a number of posties telling us they're really worried they're being required to deliver letters when they know they're a scam."

That's because the letters are easy to identify.

"They are in white envelopes, half the size of A4, between three and five Malaysian stamps, personally addressed to the recipients with the family name first, and with no return address," says Maynard.

"The amount of money being spent on stamps by the scammers over the past six years leads the Postal Workers Union to the conclusion that this is a very a successful scamming operation netting millions of dollars from New Zealand victims."

The union has made a formal complaint to the Commissioner of Police, and contacted Malaysian authorities in a bid to track the scammers down.